The present invention relates to a thermal expansion valve used for controlling the flow of the refrigerant and for reducing the pressure of the refrigerant being supplied to the evaporator in a refrigeration cycle.
A conventionally-used thermal expansion valve is formed as shown in FIGS. 4 and 5.
In FIG. 4, a prismatic-shaped valve body 510 comprises a first refrigerant passage 514 to which an orifice 516 is formed, and a second refrigerant passage 519, which are formed independently from each other. One end of the first refrigerant passage 514 is communicated to the entrance of an evaporator 515, and the exit of the evaporator 515 is communicated through the second refrigerant passage 519, a compressor 511, a condenser 512, and a receiver 513 to the other end of the first refrigerant passage 514. A valve chamber 524 communicated to the first refrigerant passage 514 is equipped with a bias means 517, which in the drawing is a bias spring for biasing a spherical valve member 518. The valve member 518 is driven to contact to or separate from an orifice 516. The valve chamber 524 is sealed by a plug 525, and the valve member 518 is biased through a support unit 526. A power element 520 with a diaphragm 522 is fixed to the valve body 510 in a position adjacent to the second refrigerant passage 519. An upper chamber 520a formed to the power element 520 and defined by a diaphragm 522 is air-tightly sealed, and within the upper chamber is sealed a temperature-responsive working fluid.
A short pipe 521 extending from the upper chamber 520a of the power element 520 is used for the deaeration of the upper chamber 520a and the filling of the temperature-responsive working fluid into the chamber 520a, before the end portion of the pipe is sealed. The extending end of a valve drive member 523 working as a temperature sensing/transmitting member which starts at the valve member 518 and penetrates through the second refrigerant passage 519 within the valve body 510 is contacted to the diaphragm 522 inside a lower chamber 520b of the power element 520. The valve drive member 523 is formed of a material having a large heat capacity, and it transmits the temperature of the refrigerant vapor flowing from the exit of the evaporator 515 through the second refrigerant passage 519, to the temperature-responsive working fluid sealed inside the upper chamber 520a of the power element 520, which generates a working gas having a pressure corresponding to the temperature being transmitted thereto. The lower chamber 520b is communicated through the gap around the valve drive member 523 to the second refrigerant passage 519 within the valve body 510.
Accordingly, the diaphragm 522 of the power element 520 adjusts the valve opening of the valve member 518 against the orifice 516 (in other words, the quantity of flow of the liquid-phase refrigerant entering the evaporator) through the valve drive member 523 under the influence of the bias force provided by the bias means 517 of the valve member 518, according to the difference in pressure of the working gas of the temperature-responsive working fluid inside the upper chamber 520a of the diaphragm and the pressure of the refrigerant vapor at the exit of the evaporator 515 within the lower chamber 520b. 
According to the thermal expansion valve of the prior art, a problem such as a hunting phenomenon was likely to occur, in which the valve member repeats an opening/closing movement.
In a prior art example aimed at preventing such hunting from occurring, an adsorbent such as an activated carbon is sealed inside a hollow valve driving member.
FIG. 5 is a vertical cross-sectional view showing the prior art thermal expansion valve in which an activated carbon is sealed therein. The basic composition of the valve shown in FIG. 5 is substantially the same as that shown in FIG. 4, except for the structure of a diaphragm and a valve drive member acting as a temperature sensing/pressure transmitting member. In FIG. 5, the thermal expansion valve includes a prismatic-shaped valve body 50, and the valve body 50 comprises a port 52 through which a liquid-phase refrigerant flowing from a condenser 512 via a receiver tank 513 is introduced to a first passage 62, a port 58 for sending out the refrigerant from the first passage 62 to an evaporator 515, an entrance port 60 of a second passage 63 through which a gas-phase refrigerant returning from the evaporator travels, and an exit port 64 for sending out the refrigerant towards a compressor 511.
The port 52 through which the liquid-phase refrigerant travels is communicated to a valve chamber 54 placed above a central axis of the valve body 50, and the valve chamber 54 is sealed by a nut plug 130. The valve chamber 54 is communicated through an orifice 78 to a port 58 for sending out the refrigerant to the evaporator 515. A spherical valve member 120 is placed at the end of a narrow shaft 114 which penetrates the orifice 78. The valve member 120 is supported by a supporting member 122, and the supporting member 122 biases the valve member 120 towards the orifice 78 by a bias spring 124. By moving the valve member 120 and varying the gap formed between the valve and the orifice 78, the passage area of the refrigerant may be adjusted. The liquid-phase refrigerant expands while travelling through the orifice 78, and flows through the first passage 62 and exits from the port 58 to be sent out to the evaporator. The gas-phase refrigerant returning from the evaporator is introduced from the port 60, travels through the second passage 63 and exits from the port 64 to be sent out to the compressor.
The valve body 50 further includes a first hole 70 formed from the upper end of the body along the axis, and a power element 80 is fixed by a screw and the like to the first hole. The power element 80 comprises a housing 81 and 91 which constitute a temperature sensing unit, and a diaphragm 82 being sandwiched between and welded to the housing 81 and 91. Further, an upper end of a temperature sensing/pressure transmitting member 100 acting as a valve drive member is fixed, together with a diaphragm support member 82xe2x80x2, to the round hole formed to the center of the diaphragm 82 by welding the whole circumferential area thereof. The diaphragm support member 82xe2x80x2 is supported by the housing 81.
The housing 81, 91 is separated by the diaphragm 82, thereby defining an upper chamber 83 and a lower chamber 85. A temperature-responsive working fluid is filled inside the upper chamber 83 and a hollow portion 84. After filling the working fluid, the upper chamber is sealed by a short pipe 21. Further, a plug body welded onto the housing 91 may be utilized instead of the short pipe 21.
The temperature sensing/pressure transmitting member 100 is formed of a hollow pipe-like member exposed to the second passage 63, and to the interior of which is stored an activated carbon 40. The peak portion of the temperature sensing/pressure transmitting member 100 is communicated to the upper chamber 83, and a pressure space 83a is defined by the upper chamber 83 and the hollow portion 84 of the temperature sensing/pressure transmitting member 100. The pipe-like temperature sensing/pressure transmitting member 100 penetrates through a second hole 72 formed on the axis line of the valve body 50, and is inserted to a third hole 74. A gap exists between the second hole 72 and the temperature sensing/pressure transmitting member 100, through which the refrigerant inside the passage 63 is introduced to the lower chamber 85 of the diaphragm.
The temperature sensing/pressure transmitting member 100 is inserted slidably to the third hole 74, and the end portion of the member 100 is connected to one end of a shaft 114. The shaft 114 is inserted slidably to a fourth hole 76 formed to the valve body 50, and the end portion of the shaft 114 is connected to a valve member 120.
According to the structure, an activated carbon is utilized, so that the time needed to achieve the temperature-pressure equilibrium between the activated carbon and the temperature-responsive working fluid contributes to stabilize the control characteristics of the refrigeration cycle.
However, the activated carbon used as the adsorbent in the prior art expansion valves were crushed carbon mainly consisting of palm or coal. The pore sizes of such activated carbon for adsorbing the working fluid are not fixed, so the adsorption quantity differs according to each carbon used. As a result, the temperature-pressure characteristics of each thermal expansion valve may be varied depending on the activated carbon used, which leads to low reliability of the valve.
Therefore, the present invention aims at providing a thermal expansion valve having a constant temperature-pressure characteristics, and which is capable of delaying its response property so as to stabilize the control of the valve. Actually, the present invention aims at providing a thermal expansion valve capable of being stably controlled, by simply changing the adsorbent to be mounted inside the thermal expansion valve, without changing the design of the conventional valve.
In order to achieve the above-mentioned objects, the thermal expansion valve according to the present invention includes a temperature sensing member and a working fluid sealed inside said temperature sensing member, the pressure of said working fluid varying according to temperature, wherein an adsorbent having pore sizes fit for the molecular sizes of said working fluid is placed inside said temperature sensing member.
Moreover, the present invention relates to a thermal expansion valve including a refrigerant passage formed to the interior of said thermal expansion valve which extends from an evaporator to a compressor constituting a refrigerant cycle, and a temperature sensing/pressure transmitting member formed within said passage having a temperature sensing function and comprising a hollow portion formed therein, said thermal expansion valve controlling the opening of a valve according to the temperature of a refrigerant detected by said temperature sensing/pressure transmitting member, wherein a working fluid which varies its pressure according to said temperature is sealed inside said hollow portion, and an adsorbent having pore sizes fit for the molecular sizes of said working fluid is placed inside said hollow portion.
Moreover, the thermal expansion valve of the present invention includes a temperature sensing pipe for sensing the temperature of a refrigerant at the exit of an evaporator constituting a refrigeration cycle, said thermal expansion valve controlling the opening of a valve according to said refrigerant temperature sensed by said temperature sensing pipe, wherein a working fluid which varies its pressure according to said temperature is sealed inside said temperature sensing pipe, and an adsorbent having a pore size fit for the molecular size of said working fluid is placed inside said hollow portion.
Further, the thermal expansion valve of the present invention includes a refrigerant passage formed to the interior of said thermal expansion valve which extends from an evaporator to a compressor, and a temperature sensing/pressure transmitting member formed within said passage having a temperature sensing function and comprising a hollow portion formed therein, wherein the end of said hollow portion of the temperature sensing/pressure transmitting member is fixed to the center opening of a diaphragm constituting a power element for driving said member, an upper pressure chamber formed by said diaphragm to the interior of said power element and said hollow portion being connected to form a sealed space to which a working fluid is sealed, and wherein an adsorbent having pore sizes fit for the molecular sizes of said working fluid is placed inside said hollow portion.
Even further, the thermal expansion valve of the present invention comprises a power element having a diaphragm being displaced according to the change in the pressure transmitted from a heat sensing pipe to which is sealed a working fluid which converts temperature into pressure, and a working shaft contacting said diaphragm at one end and displacing a valve member at the other end, wherein an adsorbent having pore sizes fit for the molecular sizes of said working fluid is placed inside said temperature sensing pipe.
According to the actual embodiment of the thermal expansion valve of the present invention, the adsorbent placed inside the valve is an activated carbon made of phenol.
Moreover, according to another preferred embodiment of the thermal expansion valve of the present invention, the adsorbent is an activated carbon having a pore size distribution with a pore radius peak in the range of 1.7 to 5.0 times the molecular size of said working fluid.
The thermal expansion valve being formed as above includes an adsorbent placed inside the temperature sensing member having pore sizes accommodated to the molecular sizes of the working fluid, which is advantageous in that the adsorption quantity of the activated carbon is constant, and the control of the valve may be stabilized.